Thin polished plates such as silicon wafers and the like are a very important part of modern technology. A wafer, for instance, may refer to a thin slice of semiconductor material used in the fabrication of integrated circuits and other devices. Other examples of thin polished plates may include magnetic disc substrates, gauge blocks and the like. While the technique described here refers mainly to wafers, it is to be understood that the technique also is applicable to other types of polished plates as well. The term wafer and the term thin polished plate may be used interchangeably in the present disclosure.
Wafers are subjects to defect inspections. Tools utilized to perform such inspections are expected to be efficient and effective. It is noted, however, that recent developments in 3D NAND technologies have challenged the efficiency and effectiveness of existing inspection tools. More specifically, because 3D NAND technologies may stack multiple layers vertically on a wafer, inspection tools designed to inspect a single planer layer do not work well when attempting to identify 3D NAND buried defects.
Therein lies a need for providing methods and systems for inspecting buried defects.